He's said it millions of times - he's looking for someone with a spark. I'm not sure Helen has displayed that. I think she's going to be another Liz Locke or Kate Walsh - good on paper and in the tasks but just not exciting enough for him to work with. I'd have thought that goes double now it's not a middle management role in his own company he's filling, but rather looking to invest money in a business the chosen candidate is going to run by themselves.
Looking at it considering what the prize actually is, then I think it has to be out of Susan or Tom. And Susan seems to have more drive and guts than Tom, as well as having a nice "self-made from nothing" story which can remind Sugar of himself. Regardless of the win/loss record, I think that the only person of the final 4 less likely to win than Helen is Jim.